zRam as swap is useful for small memory device. However, swap means
those pages on zram are mostly cold pages due to VM's LRU algorithm.
Especially, once init data for application are touched for launching,
they tend to be not accessed any more and finally swapped out. zRAM can
store such cold pages as compressed form but it's pointless to keep in
memory. Better idea is app developers free them directly rather than
remaining them on heap.
This patch tell us last access time of each block of zram via "cat
/sys/kernel/debug/zram/zram0/block_state".
The output is as follows,
300 75.033841 .wh
301 63.806904 s..
302 63.806919 ..h
First column is zram's block index and 3rh one represents symbol (s:
same page w: written page to backing store h: huge page) of the block
state. Second column represents usec time unit of the block was last
accessed. So above example means the 300th block is accessed at
75.033851 second and it was huge so it was written to the backing store.
Admin can leverage this information to catch cold|incompressible pages
of process with *pagemap* once part of heaps are swapped out.
I used the feature a few years ago to find memory hoggers in userspace
to notify them what memory they have wasted without touch for a long
time. With it, they could reduce unnecessary memory space. However, at
that time, I hacked up zram for the feature but now I need the feature
again so I decided it would be better to upstream rather than keeping it
alone. I hope I submit the userspace tool to use the feature soon.
[akpm@linux-foundation.org: fix i386 printk warning]
[minchan@kernel.org: use ktime_get_boottime() instead of sched_clock()]
Link: http://lkml.kernel.org/r/20180420063525.GA253739@rodete-desktop-imager.corp.google.com
[akpm@linux-foundation.org: documentation tweak]
[akpm@linux-foundation.org: fix i386 printk warning]
[minchan@kernel.org: fix compile warning]
Link: http://lkml.kernel.org/r/20180508104849.GA8209@rodete-desktop-imager.corp.google.com
[rdunlap@infradead.org: fix printk formats]
Link: http://lkml.kernel.org/r/3652ccb1-96ef-0b0b-05d1-f661d7733dcc@infradead.org
Link: http://lkml.kernel.org/r/20180416090946.63057-5-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zRam as swap is useful for small memory device. However, swap means
those pages on zram are mostly cold pages due to VM's LRU algorithm.
Especially, once init data for application are touched for launching,
they tend to be not accessed any more and finally swapped out. zRAM can
store such cold pages as compressed form but it's pointless to keep in
memory. Better idea is app developers free them directly rather than
remaining them on heap.
This patch records last access time of each block of zram so that With
upcoming zram memory tracking, it could help userspace developers to
reduce memory footprint.
Link: http://lkml.kernel.org/r/20180416090946.63057-4-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "zram memory tracking", v5.
zRam as swap is useful for small memory device. However, swap means
those pages on zram are mostly cold pages due to VM's LRU algorithm.
Especially, once init data for application are touched for launching,
they tend to be not accessed any more and finally swapped out. zRAM can
store such cold pages as compressed form but it's pointless to keep in
memory. As well, it's pointless to store incompressible pages to zram
so better idea is app developers manages them directly like free or
mlock rather than remaining them on heap.
This patch provides a debugfs /sys/kernel/debug/zram/zram0/block_state
to represent each block's state so admin can investigate what memory is
cold|incompressible|same page with using pagemap once the pages are
swapped out.
The output is as follows:
300 75.033841 .wh
301 63.806904 s..
302 63.806919 ..h
First column is zram's block index and 3rh one represents symbol (s:
same page w: written page to backing store h: huge page) of the block
state. Second column represents usec time unit of the block was last
accessed. So above example means the 300th block is accessed at
75.033851 second and it was huge so it was written to the backing store.
This patch (of 4):
ZRAM_ACCESS is used for locking a slot of zram so correct the name. It
is also not a common flag to indicate status of the block so move the
declare position on top of the flag. Lastly, let's move the function to
the top of source code to be able to use it easily without forward
declaration.
Link: http://lkml.kernel.org/r/20180416090946.63057-2-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge updates from Andrew Morton:
- a few misc things
- ocfs2 updates
- the v9fs maintainers have been missing for a long time. I've taken
over v9fs patch slinging.
- most of MM
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (116 commits)
mm,oom_reaper: check for MMF_OOM_SKIP before complaining
mm/ksm: fix interaction with THP
mm/memblock.c: cast constant ULLONG_MAX to phys_addr_t
headers: untangle kmemleak.h from mm.h
include/linux/mmdebug.h: make VM_WARN* non-rvals
mm/page_isolation.c: make start_isolate_page_range() fail if already isolated
mm: change return type to vm_fault_t
mm, oom: remove 3% bonus for CAP_SYS_ADMIN processes
mm, page_alloc: wakeup kcompactd even if kswapd cannot free more memory
kernel/fork.c: detect early free of a live mm
mm: make counting of list_lru_one::nr_items lockless
mm/swap_state.c: make bool enable_vma_readahead and swap_vma_readahead() static
block_invalidatepage(): only release page if the full page was invalidated
mm: kernel-doc: add missing parameter descriptions
mm/swap.c: remove @cold parameter description for release_pages()
mm/nommu: remove description of alloc_vm_area
zram: drop max_zpage_size and use zs_huge_class_size()
zsmalloc: introduce zs_huge_class_size()
mm: fix races between swapoff and flush dcache
fs/direct-io.c: minor cleanups in do_blockdev_direct_IO
...
Remove ZRAM's enforced "huge object" value and use zsmalloc huge-class
watermark instead, which makes more sense.
TEST
- I used a 1G zram device, LZO compression back-end, original
data set size was 444MB. Looking at zsmalloc classes stats the
test ended up to be pretty fair.
BASE ZRAM/ZSMALLOC
=====================
zram mm_stat
498978816 191482495 199831552 0 199831552 15634 0
zsmalloc classes
class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable
...
151 2448 0 0 1240 1240 744 3 0
168 2720 0 0 4200 4200 2800 2 0
190 3072 0 0 10100 10100 7575 3 0
202 3264 0 0 380 380 304 4 0
254 4096 0 0 10620 10620 10620 1 0
Total 7 46 106982 106187 48787 0
PATCHED ZRAM/ZSMALLOC
=====================
zram mm_stat
498978816 182579184 194248704 0 194248704 15628 0
zsmalloc classes
class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable
...
151 2448 0 0 1240 1240 744 3 0
168 2720 0 0 4200 4200 2800 2 0
190 3072 0 0 10100 10100 7575 3 0
202 3264 0 0 7180 7180 5744 4 0
254 4096 0 0 3820 3820 3820 1 0
Total 8 45 106959 106193 47424 0
As we can see, we reduced the number of objects stored in class-4096,
because a huge number of objects which we previously forcibly stored in
class-4096 now stored in non-huge class-3264. This results in lower
memory consumption:
- zsmalloc now uses 47424 physical pages, which is less than 48787 pages
zsmalloc used before.
- objects that we store in class-3264 share zspages. That's why overall
the number of pages that both class-4096 and class-3264 consumed went
down from 10924 to 9564.
[sergey.senozhatsky.work@gmail.com: add pool param to zs_huge_class_size()]
Link: http://lkml.kernel.org/r/20180314081833.1096-3-sergey.senozhatsky@gmail.com
Link: http://lkml.kernel.org/r/20180306070639.7389-3-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch has been generated as follows:
for verb in set_unlocked clear_unlocked set clear; do
replace-in-files queue_flag_${verb} blk_queue_flag_${verb%_unlocked} \
$(git grep -lw queue_flag_${verb} drivers block/bsg*)
done
Except for protecting all queue flag changes with the queue lock
this patch does not change any functionality.
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This patch converts to bio_first_bvec_all() & bio_first_page_all() for
retrieving the 1st bvec/page, and prepares for supporting multipage bvec.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
With fast swap storage, the platform wants to use swap more aggressively
and swap-in is crucial to application latency.
The rw_page() based synchronous devices like zram, pmem and btt are such
fast storage. When I profile swapin performance with zram lz4
decompress test, S/W overhead is more than 70%. Maybe, it would be
bigger in nvdimm.
This patchset reduces swap-in latency by skipping swapcache if the swap
device is a synchronous device like a rw_page() based device.
It enhances by 45% my swapin test (5G sequential swapin, no readahead)
from 2.41sec to 1.64sec.
This patch (of 4):
Commit 19b7ccf865 ("block: get rid of blk_integrity_revalidate()")
fixed a weird thing (i.e., reset BDI_CAP_STABLE_WRITES flag
unconditionally whenever revalidat_disk is called) so zram doesn't need
to reset the flag any more when revalidating the bdev. Instead, set the
flag just once when the zram device is created.
It shouldn't change any behavior.
Link: http://lkml.kernel.org/r/1505886205-9671-2-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Hugh Dickins <hughd@google.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull block layer updates from Jens Axboe:
"This is the first pull request for 4.14, containing most of the code
changes. It's a quiet series this round, which I think we needed after
the churn of the last few series. This contains:
- Fix for a registration race in loop, from Anton Volkov.
- Overflow complaint fix from Arnd for DAC960.
- Series of drbd changes from the usual suspects.
- Conversion of the stec/skd driver to blk-mq. From Bart.
- A few BFQ improvements/fixes from Paolo.
- CFQ improvement from Ritesh, allowing idling for group idle.
- A few fixes found by Dan's smatch, courtesy of Dan.
- A warning fixup for a race between changing the IO scheduler and
device remova. From David Jeffery.
- A few nbd fixes from Josef.
- Support for cgroup info in blktrace, from Shaohua.
- Also from Shaohua, new features in the null_blk driver to allow it
to actually hold data, among other things.
- Various corner cases and error handling fixes from Weiping Zhang.
- Improvements to the IO stats tracking for blk-mq from me. Can
drastically improve performance for fast devices and/or big
machines.
- Series from Christoph removing bi_bdev as being needed for IO
submission, in preparation for nvme multipathing code.
- Series from Bart, including various cleanups and fixes for switch
fall through case complaints"
* 'for-4.14/block' of git://git.kernel.dk/linux-block: (162 commits)
kernfs: checking for IS_ERR() instead of NULL
drbd: remove BIOSET_NEED_RESCUER flag from drbd_{md_,}io_bio_set
drbd: Fix allyesconfig build, fix recent commit
drbd: switch from kmalloc() to kmalloc_array()
drbd: abort drbd_start_resync if there is no connection
drbd: move global variables to drbd namespace and make some static
drbd: rename "usermode_helper" to "drbd_usermode_helper"
drbd: fix race between handshake and admin disconnect/down
drbd: fix potential deadlock when trying to detach during handshake
drbd: A single dot should be put into a sequence.
drbd: fix rmmod cleanup, remove _all_ debugfs entries
drbd: Use setup_timer() instead of init_timer() to simplify the code.
drbd: fix potential get_ldev/put_ldev refcount imbalance during attach
drbd: new disk-option disable-write-same
drbd: Fix resource role for newly created resources in events2
drbd: mark symbols static where possible
drbd: Send P_NEG_ACK upon write error in protocol != C
drbd: add explicit plugging when submitting batches
drbd: change list_for_each_safe to while(list_first_entry_or_null)
drbd: introduce drbd_recv_header_maybe_unplug
...
Patch series "writeback incompressible pages to storage", v1.
zRam is useful for memory saving with compressible pages but sometime,
workload can be changed and system has lots of incompressible pages
which is very harmful for zram.
This patch supports writeback feature of zram so admin can set up a
block device and with it, zram can save the memory via writing out the
incompressile pages once it found it's incompressible pages (1/4 comp
ratio) instead of keeping the page in memory.
[1-3] is just clean up and [4-8] is step by step feature enablement.
[4-8] is logically not bisectable(ie, logical unit separation)
although I tried to compiled out without breaking but I think it would
be better to review.
This patch (of 9):
__zram_bvec_write has some of duplicated logic for zram meta data
handling of same_page|compressed_page. This patch aims to clean it up
without behavior change.
[xieyisheng1@huawei.com: fix compr_data_size stat]
Link: http://lkml.kernel.org/r/1502707447-6944-1-git-send-email-xieyisheng1@huawei.com
Link: http://lkml.kernel.org/r/1496019048-27016-1-git-send-email-minchan@kernel.org
Link: http://lkml.kernel.org/r/1498459987-24562-2-git-send-email-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Juneho Choi <juno.choi@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Kees Cook
Minchan Kim
Linus Torvalds
Sergey Senozhatsky
Bart Van Assche
Ming Lei
Colin Ian King
Matthew Wilcox
Huang Ying